1. Field of the Invention
This invention relates generally to modular jacks such as those commonly used in telecommunications and computer networking. More particularly, this invention relates to a spring clip 9 attachable to a snap-in panel modular jack where the spring clip provides the jack with a grounded shield for electromagnetic interference (EMI) isolation and suppression when used with a shielded modular plug.
2. State of the Art
Modular plugs and jacks are widely used in telecommunications. In recent years they have also been used extensively in computer networking. These plugs and jacks are durable, reliable, and are inexpensive to manufacture with copper conductors held inside a molded plastic body. The jacks usually include a rectangular opening with at least one upper keyway. A plurality of springy copper "finger" contacts extend upward and rearward from the bottom side of the jack into the rectangular opening. A plug having a rectangular cross section, lower surface contacts bounded in channels and an upper springy key lock is insertable into the jack. The upper springy key lock on the plug engages the upper keyway in the jack while the lower surface contacts on the plug are engaged by the springy finger contacts in the jack which are maintained in proper alignment by the channels in the plug. When the plug is fully inserted into the jack, the upper springy key lock snaps into a locking position with the upper keyway of the jack. The upper springy lock of the plug extends outside the jack so that it can be pressed down against the plug to disengage the key lock from the keyway to permit the plug to be removed from the jack.
Prior art FIGS. 1a-1d show side elevation views of the open plug receiving end of four slightly different modular jacks such as those supplied by AW Industries, Inc., 6788 NW 17th Avenue, Ft. Lauderdale, Fla. 33309. Each of the jacks has a face plate 5 with a generally rectangular opening 10, an upper keyway 12 and a plurality of finger contacts 14. The number of finger contacts, the size of the rectangular opening and the number of keyways may vary according to different applications, but all of these jacks have the same general configuration as described above. Beyond the face plate 5, these jacks assume a substantially cubic or box-like shape and are provided with electrical edge card contacts 16 (FIG. 2a) at a rear portion for coupling the contacts with the gold plated fingers of a printed circuit board.
Prior art FIGS. 2a-2c show rear, top and side views of a prior art modular jack such as the AWI 7600 series designed for snap-in fitting to a rectangular hole in a chassis panel. This jack has a generally cubic shaped body 7 with a pair of forward and outward extending springy ears 18a, 18b. The jack is snap fit to a chassis panel 19 by inserting the rear end of the jack into a rectangular hole in the chassis panel. The ears 18a, 18b are biased inward towards the body 7 by the sides of the hole in the chassis panel 19 until they pass through the hole and spring back to their original position. The body 7 of the jack is dimensioned to fit through the hole and the face plate 5 is dimensioned to remain outside the hole. When the jack is snapped into the hole, the wall of the chassis panel resides between the face plate 5 and the ears 18a, 18b.
Prior art FIGS. 2d and 2e show perspective views of a plug 60 for use with a jack such as the one shown in FIG. 1d. As mentioned above, the plug 60 is provided with an upper springy keylock 64 and lower edge contacts 65.
As mentioned above, modular plugs and jacks such as those described have been used in telecommunications for many years. In most telecommunications applications, the electrical cables coupled by modular plugs and jacks are "unshielded". In recent years, however, these types of plugs and jacks have been used in computer networking to couple nodes for high speed data communication. The cables used in these applications often must be shielded from electromagnetic interference (EMI). Clearly, it would be advantageous to adapt the known modular plugs and snap-in jacks to provide a shielded coupling. To address this problem, the art has provided a shielding of the modular plug by wrapping a portion of the outer surface of the modular plug with a conductive sheath or collar, e.g. 66 in FIGS. 2d and 2e. The outer conductive sheath is arranged to contact the shielding foil or braid of the cable 62 carrying the plug. However, the art has not been as successful in providing a shielded jack. Presently, shielding of the jack is accomplished by soldering the jack to a PC board and keeping the jack within the chassis (unlike the snap-in panel jacks described above). The interior of the jack has been modified to provide an electrical coupling with the outer sheath of the shielded plug and this coupling has been ground traced to the chassis. This arrangement, however, has drawbacks. First, the plug shield coupling inside the jack is subject to untimely wear and the integrity of the coupling cannot be visually inspected. When the coupling fails, the entire jack must be replaced by desoldering and resoldering a new jack, which is time consuming. Alternatively, the entire PC board must be replaced, which is expensive. Second, because the jack is soldered to the PC board, the PC board must be supplied by the manufacturer with extra jacks which may go unused in order to provide for expansion. Alternatively, if the PC board is provided with a set number of jacks, if a user requires additional jacks, the additional jacks must either be soldered onto the board, or the board must be replaced with another PC board having additional jacks.